Introducing the music for Christmas from The Monteverdi Choir and English Baroque Soloists on BBC Radio 3 in December 2006, Sir John Eliot Gardiner elaborated on the life-changing qualities of their year-long experience: in 2000 they performed all Bach's extant church cantatas on their corresponding liturgical occasions. He suggested that any faith (not necessarily a Protestant, Christian one) is strengthened and can be mediated by this major corpus of Bach's work. The seven cantatas performed on this winning two-CD set are for the fourteenth Sunday after Trinity (BWV 25, 78 and 17) recorded in the Abbaye d'Ambronay; and for the Feast of St. Michael and All Angels (BWV 50, 130, 19 and 149) recorded in the Unser Lieben Frauen church, Bremen. They are amongst the most dramatic that Bach wrote (indeed Picander contributed text for two of them). They display Bach's ability to convey tension, high emotion and struggle without histrionics.

As we've come to expect with The Monteverdi Choir and English Baroque Soloists under Gardiner, the performances are all first rate. Perhaps the most striking quality is freshness: despite unnaturally extended and intense immersion in the music, the soloists in particular pick the listener up and guide them straight to the very core of the music. The obbligato and accompanying instrumental playing are consistently exemplary and the choral singing inspirational throughout.

Es ist nichts Gesundes an meinem Leibe (BWV 25)'. It's tempting to say that this set is worth it for the first plangent track of this cantata (first heard in August 1723) alone. It's a slow lament for the plight of humankind, actually using the affliction of leprosy as a metaphor and advancing Christ as the sole hope and salvation. Somehow the choir and accompanying orchestra (the latter always in service of the former in Bach cantatas) manage to sing 'outside' the almost mawkish words. The result is impact, not self-consciousness. Quite an achievement, and one perhaps made possible by the 'concealed' message of No 5, 'Öffne meinen schlechten Liedern', 'Open Thy ear of mercy to my poor songs'. Bach seems to be alluding to the primacy of music in confronting suffering. The implication is that the articulation of suffering with music in this very Lutheran way (leprosy has defiled us, as did the Fall) successfully draws on the superiority of music as transcendent.

Jesu, der du meine Seele (BWV 78) also begins with an emotive and heart-tugging chorale – the equal of either extant Bach Passion opening. It's followed by one of the lightest, most chuckle-inducing movements Bach surely ever wrote, an almost frivolous soprano/alto duet. Not to relieve the tension and need for catharsis. But to heighten them. Because, when followed by extremely delicately-scored recitatives and arias for tenor, it's as though we're feeling the warm, merely misty prelude to a violent summer storm. Given the subject matter (lepers' boils, disfigurements etc.) the contrast is all the more telling. As the last bass recitative and aria lead to the closing chorale, so one realizes that Bach has used technical genius to convey suffering and his (faith's) offered solution; not bombast or turgid scoring. Then you realize something else: Gardiner and his soloists and instrumentalists have brought off the most miraculous, almost operatic, diversity of musical intensity… from 'tripping' to empathetically sedate, from excited to calm. All in a little over 23 minutes. Unforgettable.

Wer Dank opfert, der preiset mich (BWV 17) sets out prize after prize. The opening fugue, the dazzling soprano aria with violin obbligato, 'Herr, deine Güte reicht', the dancing tenor aria, 'Welch Übermaß der Güte' – they all delight and are as though presented to a cyclist intent on negotiating the lavender-lined country lanes of Southern France, in which this lucid music was all recorded. But it's the stunning closing chorale – sung a cappella – that once again stops you short. The excursion may be over, but the light and clean air remain.

Nun ist das Heil und die Kraft (BWV 50 [fragment]) is something of an enigma. It certainly is a fragment. It's been speculated that the burly single three and a quarter minute chorale, which is all that's left (performance occasion unspecified) of BWV 50, may be the torso of a lost longer work; may be the embryo of an unwritten/uncompleted work; may not even be by Bach; or may be Bach's unconventional response to a cornerstone of his belief… divine salvation. At any event this is an arresting opening to the second CD in the set. It will remind you of the Sanctus of the B Minor Mass and is performed 'as is'.

Herr Gott, dich loben alle wir (BWV 130) opens with just as 'positive' and extrovert a chorale. It uses instrumental forces identical to those in the preceding BWV 50. Another very operatic cantata with battle, sword and struggle imagery, as befits the hagiography of St. Michael. It would be easy to overdo the way the music is often on tenterhooks, or to underplay the tension in order not to so to err. But Gardiner, soloists, choir and orchestra play in concert and with their minds more on Bach's mediation between doctrine and congregation/listener – with a wholly persuasive result. The Bass aria, 'Ach, wo hol ich Armer Rat' is sung as beautifully by Peter Harvey as anything in the entire set.

Es erhub sich ein Streit (BWV 19) paints more heavenly battles but ones with almost equal forces, those of good and evil. Hence 'good tunes' all round. Particularly effective is the alternation between choir, instrumental color and determined soloists. The tenor aria with chorus, 'Bleibt, ihr Engel, bleibt mir mir!', for example, is truly compelling and is the longest number on the CDs. The outcome seems never to have been in doubt thanks to the gentle and magisterial singing of James Gilchrist. But singing which doesn't overlook the need to ask for the desired outcome.

Man singet mit Freuden vom Sieg (BWV 149) moves on to victory. Written for Michaelmas, which is also a time of reflection and celebration of achievement, this cantata reworks material from Bach's 'Hunt' cantata (BWV 208). It needs a detached approach in performance – and gets one. There is no absence of engagement, though: angels still watch over humankind. And Gardiner's forces make sure they do so unobtrusively and almost as equals.

In his urbane and extremely useful (if a little hard to read: small white lettering on black) notes Gardiner makes the point that Bach knew as much 'inner turmoil' as Beethoven. Although their musical idioms are very different, Bach was just as concerned to express the soul's struggles and torture. The profound and inventive cantatas presented here have variety, commitment, drama, artistry and affirmation of life. Standing up from listening to these expert yet unaffected performances, it's hard not to feel immense closeness to Bach; one only draws away in awe at his detachment. If that is not reason enough to go right out and get this set, then just do so because of the wonderfully direct communication between musicians and listener. Unreservedly recommended.